Oil Leak BMW R1100s - calling you wrenches

Christophe Noel

Expedition Leader
In May I had all of the fluids in my BMW R1100s changed. In June I did a 3000 mile trip. I got busy and in July the bike mostly sat parked. I had to roll it out of the way last week, but certainly didn't notice any oil beneath it. Today I noticed this:


The bike has been lovingly maintained and has not once had an issue. It has just 17,000 miles on it. Any ideas? Set it on fire and buy a KLR? :)


Expedition Leader
Is it coming from the final drive hub or the rubber book on the drive shaft. Out of the hub is the final drive seal and probably the bearing. Out of the rubber boot could be the gearbox output seal.

Does it feel and smell like gearbox oil? It's not some runoff from washing and the last service.

Christophe Noel

Expedition Leader
It's most certainly running the full length of the swingarm. There's a good bit of oil forward of the transmission output, under the belly of the transmission (pic).


It's interesting to me, and maybe important information or coincidence, there wasn't so much as a drop until last week when I rolled the bike forward ten feet and then back to its original spot. Was that the tiny insult that made the output seal fail?
My 1150RT had the output seal leak at about 36k miles. If I remember correctly the dealer repair bill was $300-400. It's a simple fix, but there's a fair bit of disassembly to get to it.

Going from the S to a KLR would be cruel and inhumane punishment. You need a new Ducati instead. :roost:



Expedition Poseur
I have bad news amigo - that leak is going to be tough to fix, and it won't be cheap.

Take Mikes advise and just buy a Ducati.

In the mean time, I'll bring the trailer up and get that POS BMW out of your way. Just have the title notarized and I'll be up as soon as I get back from the land of cows and big hats.

You don't have to thank me - that's what friends are for.


Expedition Leader
First off did you do the sniff test. Gearbox oil has a distinct odor.

Now a bit of general advice. Remember this term "maintenance induced failure" alternatively know as "fix it until its f#*>{d"

Have a good look at the last stuff you worked on. Eliminate the simple and cheap things first.

I will have a better look at your photos when I get to a computer. This iPhone and my degrading eyesight are not up to the task.
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Christophe Noel

Expedition Leader
Oz, I truly appreciate your input. Same goes for Brian and his virtuous offer to relieve me of this bike.

What I have confirmed:

- The oil is for sure traveling the full length of the torque arm and pooling on the ground below the lower pivot on that torque arm. Does not appear to be brake fluid or leakage from the final drive.

- Judging by all of the dirty oil under the transmission case, this probably started during my 3000 mile trip. It appears the oil is leaking from the rear of the transmission and being blown forward and under the tranny by wind forces. (second pic).

- There seems to be a lot of soot-like residue along the underside of the boots at both ends of the swing arm.

- the bike has been parked in the same spot for the last 10 hours and does not appear to have leaked a drop. Previous Land Rover ownership leaves me to believe the gearbox is now empty. :)

Everything else on this bike seems pretty darn pristine and in good nick. And Oz, I hate to report, I can't discern if the scent is gearbox oil or not.
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Expedition Leader
OK had a better look. Hard to see anything with those photos. But if you are inclined to have a peek around here are my recommendations. (I did truthfully stay at a holiday inn express all this week :) )

What was the result of the sniff test?? Hypoid gear oil (burnt greasy frog smell) or engine oil (tattooed biker babes thighs after a 20 mile trip on a shovel head type smell)

  1. Check the drive shaft rubber boots, holes?? If there are no holes then after running your lady like white gloves around the bottom of the rubber boot check to see how oily they are. Lots of oil or does it appear to be runoff from elsewhere.
  2. Undo the hose clip and pull the boot back gently ($20 - $30 for that boot from BMW), Is there any oil inside the boot. Lots of oil inside the boot points to the gearbox output seal.
  3. No oil in the boot and you need to start looking further forward. Gearbox drain plug or front of the gearbox and leaking down the joint.
  4. Probably by now you should get the degreaser out and clean it all up. Then give it a little while and see where the oil is coming from.
  5. If you have weepage from the junction of the gearbox and engine you need to go back to the sniff test (remember that one from a lot of postings ago). If it is gearbox oil then you have a front shaft seal issue (not common). If it is engine oil you potentially have a rear main seal problem.
  6. But if it is engine oil have you gone back over the service points (sump/drain plug, oil filter etc) to make sure you didn't have any senior moments during the service.
  7. Either the front gearbox seal or the rear main seal will give your clutch a lube job it didn't ask for so lets hope its not those.

OK let us know what you find and we can make some more scientific wild arsed guesses (SWAG) and feed you all sorts of advice from our lofty perch in the peanut gallery.

Now the disclaimer: The closest bike I have to yours turned 50 this year. No oil heads in the garage anymore. I am not a BMW tech (but read the above reference to the Holiday Inn Express). I sold my last oil head a year ago and with the amount of liquid consumption damage my brain has suffered the memory may not be functioning correctly. So what I am saying is I will help you find out what could be the problem. It is up to you to decide what to do about it :bike_rider:


Expedition Leader
Ah sorry about the cross post. Hopefully my description of the smells will help you work out which one it is. Or open your fill plug on the gearbox, stick your little finger in there and compare the scents. Its a bugger I don't have anytime spare this weekend or I would take a run up and have a look. I will be up there in early Sep if you haven't sorted it by then.

Also you can usually check the gearbox oil level with a finger in the fill hole. Much easier than a rover, although from owning a few series 1 & 2 rovers and a lot of british bikes I would agree with your diagnosis (for rovers anyway). If its not leaking it is definitely empty.

Christophe Noel

Expedition Leader
Okay, so I checked the gearbox fluid level. It appears to be quite low indeed. Could be a totally separate issue, I suppose.

I tried to check inside the boot at the forward end of the driveline, but it's really tucked in there pretty tight on this bike. Hard to access it to check for fluid inside the boot.

This photo shows where the bulk of the oily residue had collected. It didn't appear to have exited the drain plug as it was clear immediately around the plug and it was sufficiently tight. I assume the oil under the gearbox was just blown forward at riding speeds.

I also noticed my oil is perhaps .5L low, but post a 3000 mile ride, I've been told that's normal.

Here's where the bulk of the oily residue was located.

I cleaned everything as best I could. I think I'll add oil to the gearbox, top off my engine oil and see if I can better assess where the leak is originating. I'm foolishly contemplating fixing this myself. I'm not a bad wrench, just reluctant.


Expedition Leader
When you are filling the gearbox with oil check with your local auto parts place and see if they have any of the UV dye to put in there. Then grab your trusty scorpion chasing UV light and use that to check around to see where it is coming from. If it oil reappears and you can see the UV tracer then it is from the gearbox. If it comes back and no UV tracer then it is engine oil. (alternatively you could use something like Royal Purple oil and just check the color but I am all for simple gadgets). I will PM my email address. Could you send me the photos in higher resolution??

Christophe Noel

Expedition Leader
I just topped off the gearbox. It has a 800 ml capacity and I was able to fit 350 ml in there. Definitely low, but it's probably been 4,000 miles since it was last checked.

My oil engine oil was low by about 300 ml as well, but again, after a 3000 mile trip, I expected that.

Now to see where the leak is.